This type of roller stand supports a cast strand coming from a strand casting mold hardened into a thin strand shell at its outer layers only, surrounding a liquid core. The liquid core extends up to the guide roller stand in a strand casting plant with support roller stand succeeding the strand casting mold, and with a drive roller stand. Consequently, the rollers must accommodate pressures from the interior directed against the strand shell from the ferrostatic pressure of the liquid metal and/or steel column depending upon their elevation level. Despite interior and exterior cooling they are subject to additional stress due to temperature change with each rotation. The roller diameter is essentially determined by bending stress and elastic flexure for rollers supported at each end in rotary bearings located outside the strand width. The roller diameter is to be kept as small as possible in order to reduce expenditures in connection with initial costs and stocking of the rollers.
The roller diameter depends primarily on the material used for the rollers and on the maximum width of the casting strand, that is, the spacing between the rotary bearings for the rollers. As a rule, the support width can be calculated on the basis of the sum of maximum casting strand width, transition from the roller body to the roller support pin, and one bearing width.
It is known in German disclosure 2 420 514 to use support rollers divided into roller sections with several bearings across the strand width rather than continuous support rollers in order to achieve casting of strands of greater width and higher casting speed. The cooling of divided support rollers, however, is made more difficult by individual roller sections which are not engaged by the strand, so that special measures must be taken in order to avoid standstill of individual roller sections. Furthermore, divided support rollers can easily dent the casting strand surface with their end edges and leave flaws affecting the quality of the cast material. The problem of eliminating strong flexure and/or great stress in support rollers is not solved by division into roller sections.
It is also known in German Trade Mark 69 28 827 that at least a number of rollers show a length which is at the most 500 mm smaller than the optimum width of the casting strand produced in the strand casting plant. The known solution only considers a part of the practical conditions of the respective state of solidification of a casting strand. Thus, over the entire length of the strand rollers of uniform length, they do not sufficiently support the casting strand in the upper part of the strand which is still hot, whereas the casting strand has too much support in the lower part which is already cooled.